If you only use one nozzle in most time, you can loose the hotend fixing screws and move the right hotend more higher than default. Or move the left side hotend down. And re-check the distance between nozzle and build plate.

to do something like this would require a redesign on the extruder carriage. the part that the hotend connects too would have to shift from the top to the bottom of the carriage. the stepper motor would also need to shift. so it is not an easy problem to solve. the system also need to be automated to move it back in place.

systems that do this likely use bowden printing so they don't have to worry about displacing the stepper motors.